Vane-type pump

ABSTRACT

The invention relates to a sliding vane type pump of the kind in which radially displaceable vanes bear against a running surface surrounding the impeller. In the prior art the running surface, which is off-set from the impeller axis, has a true circular shape. In this invention the running surface has a generally circular shape but portions on opposite sides thereof are formed as involutes of an imaginary constructional base circle. With this construction the radial displacement of a sliding vane when under load is minimized so as to effect a reduction of friction and wear.

1451 Mar. 25, 1975 United States Patent 1191 Hansen 2,165,963 7/1939 Curtis.................................418/150 8/1960 Deschamps...........................

[ VANE-TYIPE PUMP Inventor: Gunnar Lyshoj Hansen, Nordborg, 3 71] 227 H1973 Schmitz 418/268 Denmark I Danfoss A/S, Nordborg, Denmark Oct. 3, 1973 Appl. No.: 403,339

Primary E.raminer- C. J. Husar I [73] Assignee:

Assistant Examiner0. T. Sessions [22] Filed:

[30] Foreign Application Priority Data Oct. 10, 1972 Germany.1..1....................... 2249591 [52] US. 418/16, 418/150 [51] llnt. Cl. F046 1/00 vention the running surface has a generally circular shape but portions on opposite sides thereof are formed as involutes of an imaginary constructional 0 8 66 22 9 7 56 22 0 6 56 2 6 5 W W 4 m WW3 6 m2 m c 2 3 1 e11 6 0 8 dl d4 F 30; 29/156'4 WL base circle. With this construction the radial displacement of a sliding vane when under load is minimized so as to effect a reduction of friction and wear.

[56] References Cited UNITED STATES PATENTS 953,539 3 1910 Mendizibal 418/16 5 (318M595 Drawing Figures VANE-TYPE PUMP The invention relates to a vane-type pump in which the ends of the radially displaceable vanes bear against a running surface surrounding the impeller and the distance between the intake and discharge openings extending in the circumferential direction is at least equal to the distance between two vanes.

Vane-type pumps of this kind are known in which the running surface is defined by a circle disposed eccentrically of the impeller axis, the centre-point of the circle being offset from the impeller axis in the direction of the line of symmetry extending midway between the intake and discharge openings.

The following problem arises in vane-type pumps: on the one hand the vanes must reciprocate radially in suitable guides on the impeller during each revolution. On the other hand each of the vanes is subjected to the entire difference between the pressures on the pressure side and the suction side when it comes between the intake and discharge openings. This makes radial displacement difficult, and undesirable wear occurs. Both of these things can lead to the seal becoming less effectlve.

The object of the invention is to provide a vane-type pump, the capacity of which is adjustable and in which the radial displacement of each vane when under load is as small as possible. According to the invention, this object is achieved by forming the running surface on a ring which is adjustable in the rotatory direction about an axis offset from the impeller axis, and by the running surface being composed over a substantial part of its circumference by involutes ofa base circle, the centrepoint of which is the axis of the ring, and the radius of which is approximately equal to the distance between the impeller axis and the axis of the ring.

In this arrangement, the shape of the running surface is approximately that of a circle which is disposed eccentrically of the axis of the ring. Consequently rotatory adjustment of the ring leads to adjustment of the working chamber of the pump and therefore to adjustment of the pump capacity. The base circle involutes ensure that the radial displacement of each vane subjected to the pressure difference is minimal. If the ring is moved into another angular position, the favourable conditions regarding the radial displacement of each loaded vane remain substantially unchanged.

It is particularly advantageous if the axis of the ring, like the impeller axis, is disposed on the line of symmetry determined by the centres of the intake and discharge openings. In this way, not only can the capacity of the vane-type pump be varied from a maximum value to zero, but the variation can be extended through zero to a maximum value in the opposite direction of flow, the advantageous conditions being retained over a substantial part or the entirety of the angle of rotary adjustment.

Furthermore, the impeller axis may be disposed on the line of symmetry extending midway between the intake and discharge openings. In conjunction with the base circle in volutes, optimum conditions arise for this.

In a preferred form of construction the ring is mounted symmetrically, the running surface is defined by a base circle involutes on each half and over such circumferential length that it covers the distance between the intake and discharge openings at least over the major part of the angle of rotatory adjustment of the ring, and the two base circle involutes are interconnected by transition curves joining at the same tangent. The base circle involutes are preferably of such length that they are effective practically over the entire angle of rotatory adjustment of the ring in the space between the intake and discharge openings.

Parabolae for example may be considered as the transition curves. Circle segments have proved very advantageous.

A particularly preferred possible arrangement is that in which the transition curves are involutes of secondary circles which run at a tangent to the base circle on the one hand and the line of symmetry of the ring on the other.

The invention will now be described in greater detail by reference to a preferred embodiment illustrated in the drawing, in which:

FIG. 1 is a cross-section through a vane-type pump in accordance with the invention,

FIG. 2 is a longitudinal section through the pump of FIG. 1,

FIG. 3 is an illustration similar to that of FIG. 1, the running surface ring being shown at a different angle of rotatory adjustment, I

FIG. 4 is a diagram showing the form of the running surface, and

FIG. Sis a diagram similar to that of FIG. 4 and showing another form of the running surface.

The pump casing consists ofa middle part 1 with two ports 2 and 3 and two side plates 4 and 5 interconnected by screw bolts 6. The casing is completed by two cover plates 7 and 8. A shaft 11 carrying an impeller 12 is rotatably mounted in two bearings 9 and 10 secured in the side plates 4 and 5. Provided in the impeller are radial channels 13 in which blades 14 can be radially displaced. The outer ends of the vanes bear in a fluid-tight manner against a running surface 15. The running surface is formed in a ring 16, the cylindrical periphery 17 of which is guided in a complementary bore in the middle part 1 of the casing and the rotatory angular position of which can be adjusted from the exterior by means not illustrated. Intake and discharge openings 18 and 19, formed in the two side plates 4 and 5, communicate with the two ports 2 and 3. In this way, the displacement chambers 20 formed between the running face 15, the impeller 12 and each pair of vanes 14, can be filled on the suction side and emptied on the pressure side. By way of passages 21 and 22 and associated part-annular chambers 23 and 24, these intake and discharge openings 18 and 19 are connected to the radial channels in the inner faces of the vanes 14, so that the vanes can be pressed outwards by centrifugal force independently of the pump fluid.

The impeller axis M is disposed at the point of intersection of a first line of symmetry 8,, which is determined by the centres of the intake opening 18 and the discharge opening 19, and of a second line of symmetry S which extends midway between the intake and discharge openings.

The axis of rotation N of the ring 16 is offset from the axis M in the direction of the first line of symmetry 5,.

Although the running surface 15 is substantially in the form of a circle, the centre-point O of which coin,- cides with the impeller axis M in the position of the ring 16 illustrated in FIG. 1, it is composed of two involute portions between the points B and C, and A and D, and, over the remainder of its periphery of transition curves joining said involute portions at the same tangent. Thus, when the ring 16 is turned from the neutral position illustrated in FIG. 1 to another angular position (compare FIG. 3), the working chamber of the pump changes to provide a greater delivery. It will be readily seen that by rotatory adjustment of the ring 16 in the opposite direction while maintaining the same direction of rotation of the impeller 12, delivery in the opposite direction is achieved.

FIG. 4 illustrates a form of the running surface 15. The axis of rotation N of the ring 16 and the centrepoint of the running surface are shown. The latter point is disposed on a base circle K about the axis N of the ring, the radius of which is equal to the distance between the impeller axis M and the axis N of the ring. The drawing shows a mirror-image arrangement on either side of the line of symmetry S of the ring 16, Le. of the running face 15. Along the section a, the running face 15 is formed by an involute of the base circle K The evolvent is obtained for example by winding a filament about the base circle and clamping it at the point A along the line F If the filament secured to the circle K is now further wound in the clockwise direction, the end point of the filament moves on the running surface 15 from the point A to the point B where it extends along the line F The same applies in the case of the section a between the points B and C but in the mirrorimage sense.

The transition curves b and c are produced as involutes of secondary circles K, and K These circles are so disposed that the lines F and F are each at a tangent to one of them and at the same time to the base circle K and also the line of symmetry S is at a tangent to both of them. The transition curve b is obtained by winding the line F around the secondary circle K in the counter-clockwise direction until the line of symmetry S is reached. The transistion curve 0 is obtained by unwinding the line F from the secondary circle K, in a counter-clockwise direction until the line of symmetry S is reached.

In the arrangement shown in FIG. 5, the involute portions between the points A and D, and B and C are obtained in the same way as in FIG. 4. The transition portions however are circle segments d and e. To form these, the point of intersection P of the line F, and the line of symmetry S is determined and a circle segment (I having a radius equal to the distance between points P and A or P and B is drawn. The point of intersection of the extension of the line F and the line of symmetry S is similarly determined, and a circle segment having a radius equal to the distance between the points P and C or P and D is then drawn about this point of intersection. In the present embodiment the two points of intersection coincide at a point P.

If the portion of the running surface 15 between the intake and discharge openings 18 and 19 is considered in FIG. 1, then their distance from the impeller axis M changes only minimally. For practical purposes this portion can be regarded as a circle around the impeller axis. Consequently, the vanes in this portion, in which they are loaded by the difference in the pressures at the suction and pressure sides, are hardly displaced radially at all. However, on account of the involute form of the running surface, this condition also applies when the ring 16 is moved into another rotatory position as can be seen from a comparison with FIG. 3. The left-hand side of FIG. 3 shows that there are angular adjustments of the ring 16 in the rotatory direction in which the portion of the running face between the intake and discharge openings 18 and 19 is not completely covered by the base circle involute, but that a remainder thereof is covered by the transition curve. This is permissible since this condition only applies in the case of extreme angular positions of the ring 16 and/or because a considerable part of this portion of the running surface is still formed by the involute.

What is claimed is:

l. A vane type pump comprising a casing having a line of symmetry, an impeller in said casing having radially reciprocal vanes and being rotatable about a fixed axis on said line of symmetry, inlet and outlet passages on diametrically opposite sides of said casing, an adjustably rotatable ring member in said casing with the outer circumferential surface thereof having a fixed axis on said line of symmetry which is the center of an imaginary base circle and which is off-set from said impeller fixed axis, said ring member having a generally circular internal running surface with portions on diametrically opposite sides thereof which are involutely shaped relative to said base circle.

2. A vane type pump according to claim 1 wherein said inlet and outlet passages are symmetrically arranged relative to said line of symmetry.

3. A vane type pump according to claim 2 wherein said surface portions of said running surface have circumferential lengths substantially equal to the circumferential widths of said inlet and outlet passages.

4. A vane type pump according to claim 2 wherein said ring member running surface has are shaped portions separating said involutely shaped portions.

5. A vane type pump according to claim 2 wherein said ring member running surface has a second set of involutely shaped portions between said first named involutely shaped portions, said second set being involutely shaped respectively relative to a pair of circles which are tangent to each other and to said base circle. I 

1. A vane type pump comprising a casing having a line of symmetry, an impeller in said casing having radially reciprocal vanes and being rotatable about a fixed axis on said line of symmetry, inlet and outlet passages on diametrically opposite sides of said casing, an adjustably rotatable ring member in said casing with the outer circumferential surface thereof having a fixed axis on said line of symmetry which is the center of an imaginary base circle and which is off-set from said impeller fixed axis, said ring member having a generally circular internal running surface with portions on diametrically opposite sides thereof which are involutely shaped relative to said base circle.
 2. A vane type pump according to claim 1 wherein said inlet and outlet passages are symmetrically arranged relative to said line of symmetry.
 3. A vane type pump according to claim 2 wherein said surface portions of said running surface have circumferential lengths substantially equal to the circumferential widths of said inlet and outlet passages.
 4. A vane type pump according to claim 2 wherein said ring member running surface has arc shaped portions separating said involutely shaped portions.
 5. A vane type pump according to claim 2 wherein said ring member running surface has a second set of involutely shaped portions between said first named involutely shaped portions, said second set being involutely shaped respectively relative to a pair of circles which are tangent to each other and to said base circle. 